There are two major ongoing projects in my laboratory: 1. Transcription factors that establish and maintain T-cell specific gene expression. TCF-1 and HES-1 are transcription factors that impose T cell identity early in T cell development, but the mechanisms employed are uncertain, and are the focus of intense investigation in our laboratory. We currently think HES-1 represses genes involved in development of non-T cell lineages, whereas TCF-1 may drive T-lineage specific gene expression. We're using conditional alleles of TCF-1 to determine whether TCF-1 controls expression of a common set of T cell genes throughout development, or if TCF-1 instead plays different roles in mature T cells. 2. The development and function of innate lymphoid cells. Innate lymphoid cells have transcriptional programs that appear to mirror those of T cells. The comparison of innate lymphocyte cell development with T cell development provides an opportunity to understand the factors that underlie the shared as well as the unique features and functions of these apparently closely related cell lineages.